1. Field of Invention
The present invention relates to a piezoelectric element by using a thin film piezoelectric material, a piezoelectric actuator and a piezoelectric sensor including the piezoelectric element, and a hard disk drive and an ink-jet printer device provided with the piezoelectric actuator.
2. Background Art
In recent years, there is an increasing demand for a piezoelectric material becoming lead-free and research on potassium-sodium niobate ((K,Na)NbO3 (hereafter may be referred to as KNN) has become active. It is believed that a relatively high Curie temperature and good piezoelectric characteristics are obtained by KNN among lead-free piezoelectric materials and, therefore, KNN has been noted.
In addition, instead of bulk piezoelectric materials, commercialization of a piezoelectric element by using a thin film piezoelectric material has proceeded. Examples include piezoelectric sensors taking advantage of a piezoelectric effect, in which a force applied to a piezoelectric layer is converted to a voltage, e.g., a gyro sensor, a pressure sensor, a pulse wave sensor, a shock sensor, and a microphone, piezoelectric actuators taking advantage of an inverse piezoelectric effect, in which a piezoelectric layer is deformed when a voltage is applied to the piezoelectric layer, e.g., a hard disk drive head slider and an ink-jet print head, and a speaker, a buzzer, a resonator, and the like taking advantage of the inverse piezoelectric effect in the same manner.
In the case where a piezoelectric material is made into a thin film, miniaturization of an element becomes possible, applicable fields are expanded and, in addition, mass productivity increases because many elements can be produced on a substrate in one operation. Furthermore, there are many advantages in performances, for example, the sensitivity is improved in the case where a sensor is produced.    [PTL 1] Japanese Unexamined Patent Application Publication No. 2009-295786    [PTL 2] Japanese Unexamined Patent Application Publication No. 2008-192868    [PTL 3] WO 2003-070641